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# Civil Engineering/Size Limit for Pad Footings

Question

Is there a limit to the size of a reinforced concrete pad footing?

I have a 450mm x 450mm rc column carrying quite a heavy vertical load and the pad footing size is 4.3m x 4.3m x 0.85m deep. The plan area of the pad seems out of proportion when compared with the size of the column. Do we need to apply the 45 degree vertical load distribution from the column to limit the plan size of the pad footing? Is there a limit?

Thank you for your kind attention.

Regards,

CheeVui

Hi CheeVui,

The rule of thumb I use for a pad foundation is that the ratio of length/depth should be between 3 and 4. In your case it is about 5. What this means is that your rebar will be quite heavy and you may not quite get UDL reaction below the base unless the ground is not very hard, because the pressure distribution depends on relative stiffness of base and the soil.

The pad can be larger than the 45 degree distribution- this rule only applies if you wish to make the pad mass concrete (un-reinforced).
Questioner's Rating
 Rating(1-10) Knowledgeability = 10 Clarity of Response = 10 Politeness = 10 Comment Thanks again for a very clear answer.

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